氧对纳米晶铝热稳定性影响的正电子湮没研究
Influence of oxygen on thermal stability of nanocrystalline aluminum studied by positron annihilation spectroscopy
摘要：
用正电子寿命谱和X射线衍射（XRD）方法研究了纳米铝的热稳定性。这些纳米颗粒通过流动悬浮（FL）方法[1]和电弧放电（DC）方法制备。重点研究了纳米颗粒表面氧化物对结构稳定性的影响。正电子寿命结果表明，两种样品的正电子寿命τ2相对较高，晶界空位团是主要的正电子陷阱。在150 ℃时效84 h后，由表面部分氧化的纳米颗粒组成的样品的平均晶粒尺寸几乎不变，而由纯纳米Al组成的样品的平均晶粒尺寸增大。在150 ℃时效时，纳米颗粒表面的部分氧化阻碍了晶粒的生长，与Al2O3有关的空位团簇需要较长的时效时间才能分解，这意味着氧化物稳定了纳米材料的微观结构。这一效果有利于数控材料保持优良的性能。
英文摘要：
The thermal stability of nanocrystalline (nc) Al has been studied by means of positron lifetime spectroscopy and X-ray diffraction (XRD), prepared by compacting nanoparticles under high pressures. Those nanoparticles were produced by the flow-levitation (FL) method [1] and the arc-discharge (DC) method. Effect of oxide at nanoparticle surface on structure stability was investigated especially in this experiment. The positron lifetime results reveal that vacancy clusters in grain boundaries are dominant positron traps according to the high relative intensity of the positron lifetime τ2 in both samples. The mean grain size of the sample consisting of nanoparticles with partially oxidized surfaces is almost unchanged after aging at 150 for 84 h, with that of the sample consisting of pure nc Al increasing. The partially oxidized surfaces of nanoparticles hinder the growth of grain when aging at 150, vacancy clusters related to Al2O3 need longer aging time to decompose, which implies that the oxide stabilizes the microstructure of the nanomaterials. The effect is beneficial for nc materials to keep excellent properties.
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